A gasket of this type and a method for its manufacture are known, for example, from U.S. Pat. No. 4,576,859. Shielding of electronic devices is used either to shield an electronic device itself from external interfering radiation or to shield the environment from radiation which is generated by the electronic device itself, or for both purposes. Shielding of an electronic component in this way on a printed circuit board, referred to below as PCB for short, can be achieved with the aid of a cap made from an electrically conductive material which is placed over the electronic component which is to be shielded and is connected via the electrically conductive gasket to an earth wire on the PCB. The gasket is used to fill the gaps between the cap, which appears to provide a good closure, and the PCB and thus to prevent leakage of radiation.
The above-mentioned known gasket comprises a foamed body of plastic with a three-dimensional skeleton structure, the skeleton surface of which is provided with a metal covering layer, and a covering of a conductive rubber and/or plastic applied to it. This gasket is manufactured by providing an open-celled foam, for example a polyurethane foam from which the membranes have been partially removed by means of a treatment with a base, with a metal covering layer, for example by means of electroless plating of nickel. Since the original elasticity of the foam is lost as a result of the deposition of metal on the plastic foam, the metal deposit is deliberately partially broken during a subsequent deformation operation. The pores are then or simultaneously filled with a conductive rubber and/or plastic. The deformation takes place by compression of the metallized foam. The rubber is used to bind metal particles which come free, for example as a result of the deformation operation, so that they cannot come into contact with the electronic components and/or printed circuit, which could cause a short circuit.
One drawback of this known gasket, in particular the material from which it is manufactured, is its weight. After all, impregnation of the metallized plastic foam with the conductive rubber or plastic results in a relatively heavy material. In addition, there is a risk of the plastic foam ageing as a result of hydrolysis. Hydrolysis of this nature leads to the foam being crushed, during which process metal particles can come free and may cause short circuits. In general terms, the durability of the known gaskets leaves something to be desired.